The Logic Off Topic list

At 10:52 PM 2/07/01 -0700, Marvin Humphrey wrote:

>I am not an expert on the chemical composition of binder that holds the
>oxide particles to the hard drive platters.  I imagine that is a critical
>issue, as it is with tape.  However, as information density goes up,
>longevity goes down, which makes me doubt the long term viability of the HD
>format even if you could remove bearings from the equation.

Hard drives and plastic tape are completely different kettles of fish. 

Magnetic tape needs oxide particles attached to it because it is not itself
a magnetic medium. All that baking etc that you need to do with old tapes
is to do with the deterioration of the non-magnetic components -- the
binder etc. The surface of a hard-drive platter_ is_ a magnetic medium. It
doesn't need another one glued onto it. The magnetic domains that represent
the information stored on the disc are regions in the metal lattice that
makes up the coating on the hard-drive platter. How well they last I don't
know -- it probably has to do with the properties of magnetism in the metal
used and the size of the domains and what the frequency of cosmic ray
radiation is in the vicinity of the platters etc.

One issue that bears heavily on the suitablity of any digital media for
archiving  is the difficulty of finding a working drive to read them and/or
the necessary interfaces to connect them to a computer. For example -- will
a  ATA drive (parallel) from the year 2000 be connectable to any computer
in the year 2020 without resorting to custom built interface hardware? All
manner of magnetic media -- 8" and 51/4" floppy drives, backup tapes etc
are very hard to use years later for this reason even if the stored
information is not corrupt. There seems some likelihood that CD's will be
readable in backwardly compatible drives for quite some years to come (CDs
are already 20 years old next year) but sooner or later a 5 1/4" medium is
going to look very big and clumsy I suspect. 

Regards,
Murray